The gut microbiota has emerged as an important factor regulating host physiology and metabolism, in particular glucose metabolism and adiposity. Molinaro et al. did a time-resolved study on how colonization of germfree (GF) mice affects kinetics of adiposity and glucose metabolism. They found that colonization resulted in a bi-phasic glucose impairment. The first phase, occurring within 3 days of colonization (early phase) co-occurred with an inflammatory response and was independent of adiposity. The second phase, 14-28 days after colonization (delayed phase), was mostly ascribed to adipose tissue expansion and inflammation.